Continuous percolation extraction



Aug. l0, 1954 M. BoNoTTO CONTINUOUS PERcoLATIoNExTRAcTIoN Filed Dec. 20,1950

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amano: uzjmmw nza @z tujoomma ...ozmmm Q MEME Ew mwrmmwzmozou o ZMS Patented` Aug. 10, 1954 UNITED STATES ATENT OFFICE CONTINUOUS PERCOLATION EXTRACTION Michele Bonotto, Princeton, N. J.

Application December 20, 1950, Serial No. 201,782

6 Claims. 1

This invention relates to improvements in processes and apparatus for continuous percolation-extraction with solvent, and particularly to processes and apparatus for the continuous percolation-extraction by solvent of oil from oil-bearh ing materials.

This invention constitutes an improvement on the processes and appara-tus shown and described in U. S. Letters Patent No. 2,273,557 issued to appiicant on February 1'?, 1942.

in carrying out solvent extraction of vegetable seeds according to the process shown and described in rny said U. S. Patent No. 2,273,557, diniculties in relation to solvent vapors have been encountered when hot solvent or solvent near its boiling point is used. This is especially true when using an extractor with a feeding hopper through which the process material is continuously fed by gravity to a horizontal moving conveyor, the bottom of which comprises a wire screen. In Fig. 3 of said patent a moving column of material to be extracted, such as vegetable seeds in naked form, is mov-ed by gravity and fed through a feeding hopper to a horizontal rectangular trough on the conveyor beit. The trough is open at its top within an outer vaportight casing, and moves with the material beneath spraying sections in which a solvent, such as liquid paraine hydrocarbons or any other solvent in which the process material sinks, is sprayed on top of the horizontal column of material, percolates through it and collects in a container-section located below the corresponding spraying section, the solvent being then wi-thdrawn and passed on to the next spraying section in countercurrent with the moving bed or horizontal column of material under process. In this type of apparatus, when the flakes are fed con tinuously to a moving wire-screen apron-conveyor through a gravity-feeding hopp-er, the solvent vapors have a tendency to pass .through the flakes and into this hopper, and from the hopper to the atmosphere, thus 4causing loss of solvent and creating a dangerous explosive condition. While there are airlocks on the market to remedy a con-- dition of this character, they are not dependable; have a tendency to pulverize naked material and are subject to freezing.

One of the objects of this invention is to avoid the diilculties above mentioned by employing in an extractor having a belt type conveyor (through which solvent but not the process ma.- terial is permitted to pass) and which is movable through a vapor-tight casing, a gravity-feeding hopper and providing in said hopper a liquid seal so that any solvent vapors (which are released from the solvent and developed in the vapor-tight casing during extraction) are 1sept from seeping to the atmosphere through dry material or dry flakes which are being continuously fed through such gravity-feeding hopper.

I have observed that when solvent-spraying nozzles are used to nood with solvent a bed or coiunln of flakes in the several sections or stages of the moving column of material, a rela.- tively high amount of electric power is required for pump-ing to eiect pro-per spraying by keeping adequate pressure at the nozzles. Furthermore, the use o spraying nozzles has a tendency to fail in evenly flooding the bed of material, so that channeling of the solvent liquid occurs and effective extraction is impaired. Also the nozzles become clogged with ines that may occur in the miscella.

Another object of my invention is therefore in an apparatus of the type speoied to introduce in-to percolating sections (which are alternately located in relation to draining and/or diffusion sections) solvent material through a perforated surface in a solvent-container filled or partially nlled with solvent, said perforated surface being disposed over or above the top portion of the horizontally movable column or bed of iiakes and thus to provide an even rain like supply of solvent or miscella to cover and be evenly applied and sharply defined to given areas along the whole upper surface of the moving column of ila-kes as it passes under such perforated surfaces.

I have also observed that in prior art devices the rate of percloation through a bed of a given depth of akes at the. material-feeding end of the extractor (which is remote from the fresh solvent feed in a counter-current apparatus) is relatively slow as compared to the same depth of the bed further on along the extractor. This is due to the relatively high viscosity of the miscella at this point and to the counter-current action. Such rate of percolation is not only reduced by the relatively high concentration of miscella which accounts for the high viscosity, but also by the relatively low temperature of the flakes fed to the extractor which constitute the bed of material. in fact, at the feed end of the extractor the miscella is not only ygradually enriched in oil by its countercurrent progress through the apparatus, but also is further enriched in this feeding section by free oil dissolved during percolation through the fresh akes introduced into the extractor at this point.

Another object of my invention is therefore in an apparatus of the type specified to Wash in parallel current in the feeding hopper from the column of flakes the oleaginous seed oil which is freed during the iiaking or grinding operation and such wash is, in accordance with the preferred form of my invention, accomplished by providing, preferably at the material-feeding inlet or hopper of the extractor, means for building up a hydrostatic head of solvent material so that a greater quantity of such solvent material or miscella per unit of time may be recycled through the same bed than would be possible by simply flooding the bed in question. Such a hydrostatic head enables the increasing of the depth of the bed of flakes at the loading end, and fine particles sifted through the screen during the loading operation of the conveyor may be more effectively filtered through the bed when recycled with miscella in such percolating-feeding section.

I have also found that in feeding material to a moving screen, perforated conveyor or the like through a hopper located directly above such conveyor, the flow of material through the hopper is not even throughout the area of discharge and above the same because the material has a tendency7 to fill, in the first place, the fore part of the conveyor Which enters the filling area in an empty state. Consequently, to obtain an even flow of material through the feeding hopper such hopper would have to have a very narrow elongated shape, which is impractical due to arching of the material. Furthermore the percolating area is greatly reduced with the result that less G. P. M. are circulated or recycled. Furthermore, I have found that a great amount of ne solid particles contained in the ilaked material falls or is sifted through the conveyor or vvire screen during the feeding stage; that these ne particles collect in the receiver beneath the screen With the percolating miscella, and that the amount of such une particles is in proportion to the bare area of the screen on Which the flakes are fed.

Another object of my invention is, therefore, in a device or" the character specied to provide means to cause material such as flaked oil-bearing seeds to flow evenly through a feeding hopper of relatively large area and to be fed or fall directly on the Wire screen or perforated belt, and in the preferred embodiment of my invention, the material being fed is stratified during the feeding operation. This stratifying is accomplished by dividing the longitudinal area of my feeding hopper into a plurality of sections or compartments by the use of properly located and dimensioned baiiles adapted to guide the material being deposited on the belt or screen into a plurality or series of successive layers, each positioned in a higher plane above the belt or screen and starting from the line or point Where the empty screen or belt enters the bottom or open area of the feeding hopper. With such an arrangement of baiiles only a relatively small part of the material being fed through the hopper falls on the bare screen, consequently minimizing the amount of fines that may fall or sift through the screen, and also with this arrangement of haines the flow of material from and through the hopper is even and constant throughout the area of movement therethrough.

Another object of my invention is, in an apparatus of the type specified, to provide an overflow from each of the perforated surfaces hereinabove referred to and to direct such overflows to receiving containers below the spraying or deluging areas where percolated miscella is collected, such overfiovved and percolated miscella being then recirculated through perforated surfaces at a constant rate by recycling pumps so that the delivery end of such pumps is not subjected to any pressure other than the liquid head contained in the discharge conduit and the perforated surfaces are Without restriction of orifices (as is the case when spray nozzles are used), thus reducing the power required for the pumps and eliminating the clogging which occurs when nozzles are employed.

Another object of my invention is in a device of the character specified to provide in the feeding hopper above a given depth of material. being fed to the extractor a hydrostatic liquid head preferably by recycling a relatively large quantity of miscella from a liquid receiving container below the feeding hopper to a compartment above or on top of the bed or flakes in the feeding hopper and to keep this hydrostatic liquid head constant by regulating the amount of miscella in circula tion, so that a constant overflow will occur from the feeding hopper back to the receiving container from which the percolated misceila is being recycled.

With these and other objects in View the invention comprises the combination of steps and members so combined as to coact and cooperate with each other in the performance of the functions and the accomplishment of the result herein contemplated, and the apparatus comprises in one of its adaptations the species or preferred forni illustrated in the accompanying drawing in which:

Fig. l is a longitudinal section through a continuous filtering extraction apparatus embodying my invention;

Fig. 2 is a fragmentary View in horizontal section on the line 2--2 of Fig. l, looking in the direction of the arrows and showing the front portion of the apparatus illustrated in Fig. l; and

Fig. 3 is a vertical section on the line 3-3 of Fig. 1, looking in the direction of the arrows.

Referring now to these drawings which illustrate a preferred embodiment of my invention, i indicates a vapor-tight tunnel casing which may be supported in any suitable manner (not shown). Within said casing I provide a continuously-moving conveyor 2 which is preferably of the endless apron type having a Wire screen surface 2a connected with a pair of sprocket-chains 2b, each composed as shown in Fig. 3 of pairs of chain link-bars 2 arranged on opposite sides of the screen surface 2e, said chain link-oars 2C extending around and being driven by sprockets 2. Each chain includes flanged chain rollers 2d mounted on and connected with conveyor supporting rods 2e, said rollers 2d being independently supported on and running along tracks 2f mounted on shelves 2g connected with the inner surface of the casing l. The Wire screen 2a is thus stretched between said chain 2b and longitudinally disposed trough-forming stationary baffles 4 are positioned to extend along the side edges of the screen 2EL to produce an extraction trough 5 adapted to receive a horizontal column of process material 6, which when such material is aked is a fake bed.

In the preferred embodiment of my invention, the material under process comprises flaked oil bearing seeds. Handling of such flakes at the Aar feeding point is a very delicate operation because any mechanical means employed will have a tendency to break the iiakes, thus producing fines, and in the embodiment illustrated, the flaked material enters the extraction trough E of the extractor froin a surge hopper 8a passing through a star feeder 8 at a proper and suitable rate to a feeding bed A Within feeding hopper l, the lower end of which is securely connected by a vapor-tight joint with the vapor-tight casing l, and a baffle casing il positioned intermediately and connected with the star feeder 8 and the feeding hopper l conveys the flakes below the liquid level lb of a combined hydrostatic head and liquid seal 25, which, as hereinafter speciiied, is provided in said hopper l. From the surge hopper 8a the liakes are passed by gravity to feeding-bed A in the feeding hopper l, and in this feeding hopper l such feeding bed of flakes is divided into a plurality of sectional feeding columns and deposited by gravity in stratined layers on the moving upper run of wire-screen surface ze. In order to cause such iiakes to be so divided and deposited in stratified layers on said moving screen surface, I provide within said feeding hopper i a plurality of vertically-disposed material-distributing cailles lll, which extend transversely within said feeding hopper directly across and above the surface of said Wire screen and produce a plurality or series of feeding sections li, Il, lin and llc. In accordance with the preferred form of my invention illustrated, the lower edges of these baffles l, which form the top edges of a plurality of sectional feeding outlets E2, are, beginning with the baffle closest to the front of the hopper l, arranged at successlveiy increasing heights above the wire screen and form a sectional bed of flakes comprising a plurality of stratified evenly distributed layers of suitable depth, which bed is then conveyed by the conveyor screen through the vapor-tight tunnel casing E to the discharge outlet I3 thereof.

As shown, the front or feeding end of the endless screen conveyor 2 is mounted within a front compartment ib and extends to a position which is forward of the feeding hopper and when this conveyor is started the conveying screen surface 2a enters the bottom portion of the feeding hopper l in an empty or bare state at what I shall call the sifting area la. Immediately upon entry of the screen surface, a layer of iiakes will be deposited by gravity through the first of the feeding openings ll, lla, lib, ilc on the bare screen section at this sifting area. With this arrangement of bafes, therefore, only a relatively small part of the material being fed through the feeding hopper 'l' falls on the bare screen and consequently the amount of fines that may fall or sift through the screen is minimized. Also the process material or flakes will be kept in their proper place in the hopper by the baiiies lil and the depth of the first layer will be equal to the clearance space between the lower edge of the first baille lil and the wire screen conveyor Further movement of the screen area on which the first layer of flakes is then mounted will, when the screen travels below the next space between two of the baiiies iii, cause the formation of a second layer of iiakes. However, after passing the first baiiie itl the screen will not be bare but will be covered by a layer of flakes that was formed in the first section il. This first layer of flakes will thereafter prevent nes which are mixed with the flakes in the succeeding layers from passing through the screen conveyor. Successive layers will thus be laid from the sections Ila, Hb and Il, passing through the sectional feeding outlets l2 below the lower edges of the baffles. The clearance space between the lower edge of the rst bale and the conveyor will determine the thickness of the first layer deposited on the moving screen and the clearance spaces between the several edges of the second and succeeding baiiies will determine the thickness of the stratified layers which constitute the bed of flakes. Baflo Illa, which as shown comprises an extension portion of the baffle casing 9 and the length of which may be suitably regulated, will determine the iinal depth of the bed of flakes l that will ce carried on the screen conveyor throughout the length of the extractor casing,

To keep the bed of flakes A at the desired depth in the feeding hopper 7, the star feeder 8 may be revolved at the desired R. P. M. so that the quantity of flakes fed will correspond to the quantity of the extracted material discharged from the extractor casing at the discharge outlet i3.

Along the upper surface or top of said vaportight tunnel casing i and above the bed of flakes 6 so formed on the wire screen I provide a plurality or series of spraying boxes lli-Illa, Mb, iil, ldd which pass liquid solvent onto the bed of flakes within the trough 5. Such liquid solvent will then percolate through such bed of flakes, and I provide below the conveyor 2 in a position so as to receive liquid which so percolates through said bed of flakes riding on the wire screen 2a a series of receiving containers or stage receivers la, IED, itc, 45d and |58. Into one, Md, of these spraying boxes, fresh solvent is fed through conduit It and regulated by valve ISH. It is desirable in an apparatus of the type specified to provide means in the body of the casing l for causing a flow of the solvent liquid or miscella in countercurrent to the conveying movementof the process material, and into all of these boxes i4 ld solvent liquid or miscella is finally fed in such counter-current as hereinafter more particularly specified.

In order to percolate liquid from the boxes l-llld through the bed of flakes, as aforesaid, I preferably provide in said series of boxes ls-l 4d perforated surfaces 2l), and, in the preferred form of my invention illustrated, the bottoms of the spraying boxes are perforated so that the required quantity of solvent or miscella will pass through these perforations and will provide an even rain like supply of solvent or miscella to cover and be evenly applied and sharply defined to given areas along the whole upper surface of the moving column of iiakes as it passes under such perforated surfaces.

In the apparatus illustrated, I provide an overflow from the perforated surfaces 2G and boxes I--i ed hereinabove referred to and I direct such overflows into the receiving containers ifi-52 below the spraying or deluging areas where percolated miscella is received and collected. As shown, such overflow is accomplished by the conduits le and the overflowed solvent material or miscella mixed with the percolated miscella also received in such receiving containers is then supplied to the boxes lfl--llid and recirculated through the perforated surfaces at a constant rate by recycling pumps l'l-I'ld in such manner that the delivery ends of such pumps are not subjected to any pressure other than the liquid head in the connected conduits and as the perforated surfaces are without restriction of orifices,

7 as is the case when spray nozzles are used, the power required for the pumps is reduced. Also the clogging of the orifices with fines that occur in the miscella is substantially avoided and reduced over prior art nozzle devices.

The overow from each of the spraying boxes Ill-I4d directly through conduits lil-I9d back to the receiving containers or stage receivers IE-Id causes the liquid supply or body in such spraying boxes Ill-Ill(1 to be kept constant and the level I6b thereof to be maintained, and this maintenance of liquid level in the spray boxes will cause a uniform rain even if the spray boxes are not supported in truly horizontal positions.

The quantity of percolated liquid comprising miscella supplied as aforesaid by the pumps I'Z-i'id to the spraying boxes Ill- Idd and thus recirculated through the spraying boxes is preferably adjusted when necessary by blinding a portion ci the periorations according to requirements rather than by throttling the discharge of the stage pumps I'I-Ild.

In the embodiment of my invention illustrated, a series of solvent heaters 2li-24c are applied to conduits which conduct fresh solvent and miscella in steps of the counter-current movement thereof, and, as shown, such heaters 25 are applied to the fresh solvent conduit I5 and the pump-delivery conduits 2I, 2la and ZI". Obviously the fresh solvent in conduit I6 and miscella in conduits 2i, 2Ia and 2ib being supplied to the boxes Ill- 4d may be heated to any desired temperature by the heaters 24--211c and solvent vapors 26 above the bed 6 of akes will be produced.

To start the percolation-extraction operation in the casing body I, the feeding hopper 'I is rst filled with process material or ilakes. Then the conveyor screen 2a is started at a proper speed until the bed ofl flakes in the extractor casing reaches a point below the spraying box Illd adjacent to the discharge outlet. Movement of the conveyor is then stopped. Fresh solvent of the desired temperature is then fed continuously at a proper rate into said spraying box Idd and the solvent percolated from this box Md is collected in the stage receiver I5e and is then recirculated by the pump Il to said box Md. When the stage receiver I5e is full, percolated solvent which will contain some oil in solution and may properly be called miscella will overliow through conduit i8 from said stage receiver I5e to the next adjacent stage receiver Id. When the necessary quantity of liquid is collected in the stage receiver 25d the pump Ila is started and the miscella is pumped to the box la. From the box MC the miscella will drop through the perforations in the bottom thereof to the upper surface or top of the bed of akes and after percolation therethrough will be collected in the stage receiver d and will from that stage receiver be recycled through the pump Via to the box 14C. When the stage receiver 55d is full, the miscella will overflow and pass by conduit 18a to the stage receiver I5c and from there through the pump IIb will be recirculated to the spraying box Illb from which it will percolate through the bed of flakes back through the stage receiver 150 and when this stage receiver Iic is full, the miscella will overflow and pass by conduit I8b into the stage receiver Ib and so on, the pumps after starting being kept going.

I have found that it is desirable and important that divisions or gaps be located between the several spraying boxes through which the solvent and miscella are percolated to provide what in my above-mentioned patent I have called diffusion zones, as they provide also a means for partial or total draining (according to the length of such divisions or gaps) of the miscella from the bed of flakes before the material during its travel in counter-current toward the outlet of the apparatus reaches the next zone of percolation or ilooding through which the miscella of less concentration is sprayed.

It will be noted that in Fig. l the miscella draining through the diiiusion or draining sections falls into the stage receiver which is positioned below the corresponding spray box and that these stage receivers are designed or so arranged and extended as to collect miscella from the spraying box or section directly above it and from an adjacent draining section. For example, the stage receiver I5e will collect miscella percolating through the box Id and part of the miscella draining from the diifusion or draining section I".

The stage receivers will ll successively and will overiiow because fresh solvent entering the box ld is continuously ied at a given rate and, as aforesaid, moves through the body of the casing I in counter-current to the movement of the process material. During this travel, the solvent picks up oil to form a miscella which gradually increases in oil concentration so that when mscella reaches an area below the first spray box It, I preferably provide means, such as conduit IBG, whereby the miscella by-passes said stage receiver Ia and iiows to the stage receiver I5 beneath the hopper l.

By the pump Il'e solvent material or miscella is fed from the stage receiver I5 to a compartment 22 in the top portion of the feeding hopper 'i in which the flake bed A is provided and forms therein the combined hydrostatic head and liquid seal 25. This bed of flakes A is kept constant as far as possible and the depth thereof will depend upon the physical characteristics of the material under process Which will preferably be prepared so as to present a known resistance or friction to the flow of solvent through the bed.

The rate of percolation through the bed of nakes A on the screen 2a, which as aforesaid is of predetermined depth, will be regulated so as to always keep the hydrostatic head 25 of miscella above or on top of the bed of :flakes A. This hydrostatic head 25 will partially fill the feeding hopper l and will act as a liquid seal so that the solvent vapors 2B which are released from the solvent and contained in the vapor-tight enclosing casing I in which the conveyor operates will be kept from seeping to the atmosphere through dry material or dry akes, which would conventionally be continuously fed through such feeding end oi the hopper if such material were not kept immersed in liquid. rIhis arrangement will enable the heating at the :final stages of extraction of the solvent and the miscella to a point near the boiling point thereof, thus greatly facilitating the extraction operation.

It will be understood, that preferably only the fresh solvent or weak miscella is heated to facilitate the complete extraction and diffusion (in the stages near the discharge end) and the temperature of the solvent is gradually decreasing (from the inlet to the outlet) due to the presence of cold ilakes at the inlet. The pure solvent also loses temperature in supplying heat to the bed of flakes while they travel toward the exit or outlet. The temperature of the miscella used by me as a seal, therefore, is near to the temperature of the material or flakes when they enter the hopper.

As shown, provide a heater 24 on the fresh solvent conduit it and also apply heaters 24e, 261 and 2d@ on the recycling conduits 2 I, 2te and 2lc from the pumps Il, Ila and Hb? An overflow will be located so as to keep the hydrostatic head 25 at a desired level '5b and the solvent material or miscella therein will move through the process material in the hopper in parallel current with the feeding movement oi said material.

This hydrostatic head will assist also in overcoming the friction encountered by the miscella during percolation through the bed of flakes A, which in the feeding hopper is deeper than on the apron conveyor. Said hydrostatic head will also overcome resistance to percolation due to the high viscosity of miscella at the forward or feeding end of the extractor. Also, during the recycling in the feeding hopper the free oil liberated from the seeds during the flaking operation Will be completely Washed out of the flakes and a high concentration of miscella will be procured.

When a solvent of higher specific gravity than the material under process is used, as for example trychloroetylene, a hydrostatic head may be provided even in this case if a relatively high concentration of the miscella used for the hydrostatic head is employed in which the material will sink.

ln accordance with the preferred form of my invention, when the stage receiver i5 beneath the feeding hopper 'i is filled, the miscella therein will overoy in the reverse direction. This reverse flow is desirable because When the extractor operates continuously a certain amount of fine particles will sift through the Wire screen during the loading of the screen conveyor and these fine particles are only partially filtered during the recycling of the iniscella through the feeding hopper '1. Such lines are thus collected beneath the hopper in said stage receiver l5 and when the stage receiver i5 overflows reversely to the stage receiver les will be recycled with the miscella by the pump Hd through the spray box llia to the top or upper surface of the moving bed of flakes on the screen conveyor.

After the operation of loading the flakes from the hopper no more nes will be sifted through the screen because the bed of flakes will not be further disturbed after such flakes leave said feeding section.

In the preferred form of my invention, when the stage receiver liL is filled, miscella subsequently added from an overflow conduit le and from the receiver l5 will leave said stage receiver l5a and the extractor through overiios1 conduit 2l and from this conduit such miscella will pass to distillation means for the separation of the oil from the solvent.

The above described operation Which is desirable to prime the extractor will continue for a length of time depending upon the characteristics of the material under process, and preferably a sample of the material taken from the bed of flakes under the spraying box ldd adjacent to the discharge opening E3 Will be procured and examined or analyzed to show the extent of the extraction that has been reached.

After the aforesad priming, the conveyor is then started at a proper speed to provide the necessary time required for extraction. Such time is normally from six to twelve inches per minute. When the extractor is in equilibrium, the traveling bed of flakes is thus submitted to counter-current extraction because the flakes on Vthe conveyor pass under the deluging areas through which misoella of increasing concentration percolates; the richer miscella thus percolating through the section nearer the feeding end and the leaner miscella percolating through the section nearer the discharge outlet. The fresh solvent thus percolates through the spent flakes at the discharge end.

The length of the apparatus may be considerably shortened and the time of extraction correspondingly reduced by subjecting the extracted flakes leaving the apparatus to a squeezing action in squeezing devices such as shown and described in Patents Nos. 2,184,248 and 2,203,665 issued to applicant, and through which devices the larger part of t e solvent held up physically inside the flakes may be liberated in a liquid state by mechanical pressure. Thus, the extracted flakes on their Way to the solvent elimination phase of the process Will contain much less solvent than if the flakes were subjected only to draining action at the exit of the extractor. Such draining time would of necessity be relatively long and, of course, extra length of the apparatus would have to be provided for such purpose. 1t will be understood that the less solvent retained by the flakes means less steam used in eliminating the solvent from the extracted flakes during the solu vent-elimination step.

In some cases a squeezing action to remove solvent retained might not be desirable, and in such cases it may be desirable to let the solvent drain by gravity from the bed of flakes before it reaches the discharge outlet. In such cases, the length of the rear end la of the conveyor to the rear of the box ldd may be increased to provide it for such drainage, and in such cases the drained liquid will be collected in the stage receiver extending in the rear stage container, which of course would be extended for this purpose or if desired an additional receiver might be provided.

As shown, the casing l at the rear end is provided With a conventional vent 2S which leads vapors from said rear end to a condenser or other ,f suitable outlet therefor, and a similar vent 29 is provided in a process-material conduit 3d which connects With and is positioned between the star feeder 8 and the baille-casing 9.

As illustrated, the baille-casing s extends into the feeding hopper l' and the compartment 22 for the hydrostatic head 25 is formed between the outer wall or surface of said baille-casing S and the inner wall or surface of the feed hopper l.

It will be understood that the vent 29 leads to a condenser such vapors as are formed in the hopper l and that pass through the flakes in the baille casing 9.

Having described my invention, I claim:

1. A process for continuous percolation extraction with solvent in systems of the horizontal screen-conveyor type consisting in feeding down- Wardly by gravity through a feed hopper a column of oil-bearing process material, guiding said column of process material laterally from said hopper, :passing through the hopper and in parallel current with said process material a volatile liquid solvent to Wash out from the process mate rial the oil which is freed during operations of preparing such solid materials for extraction and forming in said hopper a liquid seal of said solvent above said process material to keep solvent vapors formed in the process from seeping through the process-material at the inlet thereof.

2. A yprocess for continuous percolation extraction with solvent in systems of the horizontal screen-conveyor type, the steps of passing solid oil-bearing process vmaterial downwardly by gravity through a feed hopper, guiding such oil-bearing process material laterally from said hopper, forming above said solid oil-bearing process material being fed a hydrostatic head of volatile liquid solvent material, passing such volatile liquid solvent material under pressure of said hydrostatic head through said process material being fed in parallel current to the gravity movement thereof, whereby a greater quantity of such solvent liquid per unit of time may be passed through said bed than would be possible by simply flooding the bed.

3. A process for continuous percolation extraction with solvent in systems of the horizontal screen-conveyor type, the steps of passing solid oil-bearing process material downwardly by gravity through a feed hopper, guiding such process material laterally from said hopper, forming above said solid process material being fed a hydrostatic head of volatile liquid solvent material, passing such volatile liquid solvent inaterial under pressure of said hydrostatic head through bed of said solid oil-bearing process material being fed in parallel current to the gravity movement thereof, whereby a greater quantity of solvent liquid per unit or time may be passed through said bed than would be possible by simply flooding the bed, receiving and aggregating below said body of solid oii-bearing process material the volatile liquid solvent so fed from the hydrostatic head and recycling such aggregated solvent to said hydrostatic head.

4. A process for continuous percolation ex traction with solvent in systems of the horizontal screen-conveyor type, the steps of passing solid oil-bearing process material downwardly by gravity through a feed hopper, guiding such process material laterally from said hopper, forming above said solid process material being fed a hydrostatic head of volatile liquid solvent material, passing such volatile liquid solvent ma terial under pressure of said hydrostatic head through a bed of said solid oil-bearing process material being fed in parallel current to the gravity movement thereof, whereby a greater quantity of solvent liquid per unit of time may be passed through said bed than would be possible -by simply flooding the bed, receiving and aggregating below said body of solid oil-bearing process material the Volatile liquid solvent so fed 12 from the hydrostatic head and recycling such aggregated solvent to said hydrostatic head and maintaining said hydrostatic head of material at a given level by causing an overflow of solvent material above said level.

5. In a process for continuous percolation extraction with a volatile solvent in systems of the horizontal screen-conveyor type, the steps of feeding a body of solid oil-bearing process material by gravity to a conveyor, dividing the body of oil-bearing process material being fed into a plurality of successive transversely registering columns of varying heights, one behind the other, and conveying such columns of said oil-bearing process material in a direction toward a discharge opening through feed openings arranged in planes one above the other to produce a bed of stratied layers of such oil-bearing process material in varying positions one above the other.

5. In a process for continuous percolation extraction with a volatile solvent in systems of the horizontal screen-conveyor type, the steps of feeding solid oil-bearing process material by gravity through a hopper to provide a body of such oil-bearing process material for conveyance, dividing said solid oil-bearing process material into a plurality of successive transversely registering columns, feeding for conveyance by said conveyor a relatively narrow layer of said oilbearing process material from the rst of said successive columns to minimize the bare faces of the screen conveyor and reduce 'the quantity of lines passing therethrough during the feeding of such process material to said conveyors and simultaneously feeding process material from another column above said first layer.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 654,170 Malard July 24, 1900 813,078 Bernhardt Feb. 20, 1906 1,411,154 Bollmann Mar. 28, 1922 2,550,947 Straight May 1, 1951 2,551,820 Woody et al May 8, 1951 2,585,473 Kennedy Feb. 12, 1952 FOREIGN PATENTS Number Country Date 218,522 Germany Feb. 1,. 1910 74,042 Switzerland July 24, 1916 

1. A PROCESS FOR CONTINUOUS PERCOLATION EXTRACTION WITH SOLVENT IN SYSTEMS OF THE HORIZONTAL SCREEN-CONVEYOR TYPE CONSISTING IN FEEDING DOWNWARDLY BY GRAVITY THROUGH A FEED HOPPER A COLUMN OF OIL-BEARING PROCESS MATERIAL, GUIDING SAID COLUMN OF PROCESS MATERIAL LATERALLY FROM SAID HOPPER, PASSING THROUGH THE HOPPER AND IN PARALLEL CURRENT WITH SAID PROCESS MATERIAL A VOLATILE 